MOF-derived Co3O4 nanosheets rich in oxygen vacancies for efficient all-solid-state symmetric supercapacitors

Co3O4 is a promising pseudocapacitive material with a high theoretical capacity. We demonstrate herein a facile interfacial engineering toward Co-metal organic frameworks (Co-MOFs) derived Co3O4 nanosheets for improving the overall capacitive performance. Firstly, a thin hydrophilic carbon layer was coated onto carbon cloth (CC) to stablize the interfacial coordination effect between Co3O4 and carbon fibres. Secondly, oxygen vacancies by reducing Co3O4 was introduced to improve the electron and ions transfer on the interface between Co3O4 and electrolyte. The unique Co3O4 structure and composition endow the optimal v-Co3O4/CC composite with significantly improved specific capacity (414 C g(-1) at 1 Ag-1) and excellent stability (0.00174% capacity loss per cycle for 15000 cycles). Asymmetric supercapacitor by assembling v-Co3O4/CC composite as positive electrode with the same MOF derived carbon nanosheets as negative electrode demonstrates a high volumetric and gravimetric energy density of 0.74 m Wh cm(-3) (14.7 mW cm(-3)) and 45.3 Wh kg(-1) (915 Wkg(-1)), respectively. This work might provide a simple but efficient approach for boosting the pseudocapacitive performance of transition metal oxides. (C) 2019 Elsevier Ltd. All rights reserved.